Acoustic signaling apparatus



NOV. 5, 1935. BRODEN 2,019,595

ACOUSTIC SIGNALING APPARATUS Filed Sept. 18, 1953 s Sheets-Sheet 1 Nov. 5, 1935. J. G. M, BRODEN 2,019,596

ACOUSTIC SIGNALING APPARATUS Filed Sept. 18, 1933 3 Sheets-Sheet 2 5 92):):323121."WI/1 4,, A nu v U o I five/77a 26 \f. W g "00 61? v 75? LAW a Nov. 5, 1935. J, G M BRODEN v 2,019,596

ACOUSTIC S IGNALING APPARATUS Filed Sept. 18, 1933 3 Sheets-Sheet 3 1/; wen/ 4 Patented Nov. 5, 1935 UNITED STATES ATENT OFFICE.

Application September 18, 1933, Serial No. 690,019 In Sweden September 28, 1932 Claims.

This invention relates to an acoustic signaling apparatus comprising two or more sound-emitting devices of the type having an oscillating or vibrating member such as a membrane or spring- 5 pressed or weighted piston, driven by an elastic pressure fluid under pressure such as compressed air or steam.

As isiwell known in the art, if two or more acoustic signaling devices which are constructed or tuned to emit sound waves of the same frequency and which operate in fixed phase relation to each other, are placed at fixed distances from each other, which distances are adjusted according to the wavelength of the sound waves emitted,

it is possible, through control of the interference between the waves, to increase thesoundwave energy in a certain direction and toreduce the energy sent in other directions. This phenomenon has been utilized in certain instances, and in the case of electrically-operated diaphragm vibrators no difiiculty-has been encountered in securing the necessary fixed relationship, or coincidence between the spaced sound-emitting devices so far-as concerns. frequency andphase of the vibratory motion of the-sound-emitting diaphragm vibrators, especially; since they can be connected either in series or in-parallelwith a common source of electric current.

However: great difliculties heretoforewereencountered when it was desired to obtain-a similar result, with fluid driven sound-emitting devices which each have an oscillating or vibratingmembersuch, as a membrane or spring pressed or weightedpiston which operates at a natural; fre- 3 altemately open and close an outlet for said fluidinto a horn orlike sound-producing or-magnifying device. These diflicultieswere dueto the fact. that, while it was possible to construct or tune the sound-emitting devices foremitting sound wavesof practically the same frequency, nevertheless in most cases: it proved practically impossible to secure thenecessary coincidence-or fixed relation between the sound-emitting devices spaced apart from each other, as concerns the phase of the oscillatory or vibratory motion of the oscillating of vibrating members.

These diificulties are avoided by the present invention, according to which thespaced soundemitting devices have their oscillating or vibratingmembers coupled with each other through a common-resonator or resonator system in such manner as to force the vibrating or oscillating members tooperate not only at the same frequency but also in such a fixed phase relation quency under the action of thedriving fluid; to

to each other as will result in the desired'effect being obtained; It is evident that the soundemitting devices should be constructed or tuned for emitting sound waves of practically the same wave length; but according to the present. in- 6:5.

vention the necessary exact coincidence between the sound-emitting devices-as concerns the frequency and phase of the oscillatoryor vibratory motion of the oscillating or vibrating members is obtained'automatically due to the coupling of 10 these members to the common resonator or'resonator system in such-a manner that thesemembers will be acted on by parts of the wavecolumn in the-resonator system which are of precisely the same phase. It is evident that this resonator 16; or resonator system should'be resonant to the natural frequency of the oscillating or vibrating members of the. fluid-driven signaling: devices, and the resonator may be connected in the supply conduit forthe pressure fiuidso that this 20v fluid flows through the resonator or resonator: system to: the oscillating or vibrating members which control the outlets forthe saidfiuid into the horns or the like. But the-vibrating or-oscillating-members can also be coupled to the com- 25;.

mon resonator or resonator system in such a manner that the energizingfluid does not'flow through the resonator or resonator system. The oscillating n-r vibrating members should be coupled to the resonator or resonator system atpointsflO separated from each other eitherbya complete wave length or-by an integral member of complete wave lengths ofthe stationary wave occurring in the resonator or resonator system, which latter should be soconstructed as to have one of its nodal points equally distant from cache! the oscillating or vibrating members.

The invention will now be more fully describedwith reference to the accompanying'drawlngs in which Figs. 1, 2, 3, and-4 are diagramsot Iour different forms of the invention. Fig. 5 is an elevation showing the rear side of an embodiment of the invention, and Fig. 6 is a section thereof substantially on the line A-A in Fig. 5-; Fig. '7' is a view similar to Fig. 5*of another embodiment of the invention, and Fig. 8 is a section thereof substantially on the line BB in Fig. '7.

Referring first to Fig. 1, they reference numeral 5 indicates the sound-emitting devices, each 01 which consists of a horn or the like-and is pro- 50.;

videdwith an oscillating orvibrating member 2 in the form of a membrane or the like adapted 1 to be driven by a fluid such as compressed air or steam. The membrane or the like alternately opens and closes an outlet for the fluid into theta horn or the like, as is well known in the art. The two sound-emitting devices I have their inlets for the pressure fluid interconnected by means of a pipe 3 which over part of its length is surrounded by an outer pipe 4. A supply pipe 5 for the fluid for both sound emitting devices I is connected to the said outer pipe 4. The space between the pipes 3 and 4 communicates with the interior of the pipe 3 through holes 6 in the wall thereof.

In this embodiment the pipe 3 forms a resonator common to both sound-emitting devices I. The stationary wave motion occurring in this resonator will have a node at the middle point of the pipe 3 and antinodes at the holes 6, these holes serving to fix the positions of v these antinodes. The stationary wave will also have nodal points at or near the membranes 2. Consequently, the membranes 2 are distant about one complete wave length of the stationary wave which occurs in the resonator pipe 3, from the middle of the said pipe 3; and the said stationary wave will be of the same phase at each of the membranes 2 whereby the membranes 2 will be forced to operate in synchronism.

The form of the invention shown in Fig. 2 differs from the foregoing in that the resonator pipe I which interconnects the driving fluid inlets of the two sound emitting devices has its ends opening into inlet chambers 8 connected to a common supply conduit 9. In this form, like that of Fig. 1, the stationary wave occurring in the resonator pipe will have nodes at the middle point of the resonator pipe and at or in the proximity of the membranes 2. In the form shown in Fig. 3 each of the sound emitting devices I is provided with a spherical resonator I0, and the two resonators I are interconnected through an intermediate resonator II. which preferably also is a spherical resonator, but can if desired have the form of a tube resonator. In this form of the invention the common supply conduit I2 for the fluid preferably is connected to the intermediate resonator II. The membranes 2 of the soundemitting devices are so spaced as to be acted upon by parts of the wave column which are in the same phase, and, consequently, the membranes 2 are separated by an integral number of complete wave lengths of the stationary wave in the resonator system.

In the form. of the invention shown in Fig. 4 chambers I3 at the rear sides of the membranes 2 of the sound-emitting devices I are interconnected through a resonator pipe I4 surrounded over a part of its length by an outer pipe I 5 and communicating therewith through holes I6 near the closed ends of the outer pipe I5. The ends of the inlet pipes II for the fluid abut the front sides of the membranes 2 and are connected to a common supply conduit I8. The stationary wave occurring in the resonator pipe I4 will have antinodes at the openings I6 and nodes at the middle point therebetween and at'or near the membranes 2.

In all forms of the invention shown in Figs. 1 to 4 the two sound-emitting devices I are placed at a distance equal to a half wave length of the sound waves which are produced, and the two sound-emitting devices have their horns arranged in the same direction.

'said devices, which are provided with the mem branes 2 and are of a well-known construction; The casings 21 of the sound-emitting devices I' are connected to the tubular stand 26 by means of flanges I9, and they are interconnected through the common resonator pipe 20. 5 The embodiment of the invention illustrated in Figs. 7 and 8 comprises a U-shaped tubular frame 2I carrying four sound emitting devices I placed one above the other at distances equal to a half wave length. Each of the sound-emitting devices 10 is provided with a pair of diametrically opposed casings or inlet tubes 22 connected to the respec"* tive branches such as the tubular trans-e1 2| by means of flanges 23 or the like. All the seundemitting devices are connected in series thrtiu'gh 115J resonator pipes 24 which interconnect the dais ings or inlet pipes 22 of the sound-emitting (is vices as shown, so that each sound-emitting de-' vice is coupled with each adjacent sound-emitting device through a resonator common to two of the four sound-emitting devices. One of the casings or inlet pipes of the lowermost and the uppermost sound-emitting device is provided with a tubular resonator 25 closed at its outer end.

The invention is not concerned with the construction of the sound-emitting devices per se, 1 which canbe of any known or suitable kind. For instance the sound-emitting devices may also be of the well kiiojv'ri type having instead of the membrane herein shown, a spring pressed or weighted piston capable of performing an oscillatory motion at a natural frequency under the action of the fluid.

What I claim and desire to secure by Letters" Patent is:-- 1. An acoustic signaling apparatus comprising in combination a, plurality of pressure fluid drivensound-emitting devices each having a member capable of performing an oscillatory motion at a natural frequency under the action of the driving 40 pressure fluid, for alternately opening and closing an outlet for the said fluid, and a resonator sys tem common to the said sound emitting devices and resonant to the natural frequency of the oscillating members thereof, said oscillating mem V bers being coupled to the common resonator system in such a manner as to be acted on by parts of the wave column in the resonator system which are of precisely the same phase, whereby to secure exact coincidence between the sound emitting devices in respect to frequency and phase of the oscillatory members thereof, the oscillating members of the pressure fluid driven sound-emitting devices being coupled to the common resonator system at points separated by an integral number of complete wave lengths of the stationary wave I occurring in the resonator system, the resonator system being so constructed as to have one of its nodal points equally distant from each of the oscillating members coupled thereto. 2. An acoustic signaling apparatus comprising in combination a plurality of pressure fluid driven sound-emitting devices each having a member capable of performing an oscillatory motion at a natural frequency under the action of the driving pressure fluid, for alternately opening and closing an outlet for the said fluid, and a resonator system common to the said sound emitting devices and resonant to the natural frequency of the oscillating members thereof, said oscillating members being coupled to the common resonator system in such a manner as to be acted on by parts of the wave column in the resonator system which are of precisely the same phase, whereby to secure exact coincidence between the sound emitting devices in respect to frequency and phase of the oscillatory members thereof, chambers being provided at the rear side of the oscillating members of the sound emitting devices which chambers are interconnected through the common resonator system, while the outlet ends of supply pipes for the driving fluid abut the front side of the oscillating members.

3. An acoustic signaling apparatus comprising in combination a plurality of pressure fluid driven sound-emitting devices each having a member capable of performing an oscillatory motion at a natural frequency under the action of the driving pressure fluid, for alternately opening and closing an outlet for the said fluid, and a resonator system common to the said sound emitting devices and resonant to the natural frequency of the oscillating members thereof, said oscillating members being coupled to the common resonator system in such a manner as to be acted on by parts of the wave column in the resonator system which are of precisely the same phase, whereby to secure exact coincidence between the sound emitting devices in respect to frequency and phase of the oscillatory members thereof, said resonator system comprising spherical resonators, one for each of the sound-emitting devices, said spherical resonators being interconnected through an intermediate resonator provided with an inlet for the driving pressure fluid.

4. An acoustic signaling apparatus comprising in combination a plurality of pressure fluid driven sound-emitting devices each having a member capable of performing an oscillatory motion at a natural frequency under the action of the driving pressure fluid, for alternately opening and closing an outlet for the said fluid, and a resonator system common to the said sound emitting devices and resonant to the natural frequency of the oscillating members thereof, said oscillating members being coupled to the common resonator system in such a manner as to be acted on by parts of the wave column in the resonator system which are of precisely the same phase, whereby to secure exact coincidence between the sound emitting devices in respect to frequency and phase of the oscillatory members thereof, and inlet chambers for the driving fluid to the oscillating members of the sound-emitting devices, provided on the latter, the said resonator system comprising a resonator pipe by which said chambers are interconnected, said chambers also being separately connected to a supply conduit for the driving pressure fluid.

5. An acoustic signaling apparatus comprising in combination a plurality of pressure fluid driven sound-emitting devices each having a member capable of performing an oscillatory motion at a natural frequency under the action of the driving pressure fluid, for alternately opening and closing an outlet for the said fluid, and a resonator system common to the said sound emitting devices and resonant to the natural frequency of the oscillating members thereof, said oscillating members being coupled to the common resonator system in such a manner as to be acted on by parts of the wave column in the resonator system which are of precisely the same phase, whereby to secure exact coincidence between the sound emitting devices in respect to frequency and phase of the oscillatory members thereof, each sound-emitting device being coupled with each adjacent soundemitting device, through a resonator common to two of the sound-emitting devices, so that all the sound-emitting devices are connected in series through the resonators.

JOHN GUSTAF MAURITZ BRQDEN. 

